Ok so i have a few .mkv video files. Video file A..= 1080p and wont play B=720p will play but no sound B= after i split mkv and redid sound video and sound play.But volume way to low. barly can hear. C= unmodded 720p both video and sound play but again volume to low. So my question is what type file does it play that are 1080p.? How to fix said problems?